int dragX, dragY, moveX, moveY;
void setup() {
  size(100, 100);
  noStroke();
  fill(0, 102);
}

void draw() {
   background(204);
  fill(0);
  ellipse(dragX, dragY, 33, 33); // Black circle
  fill(153);
  ellipse(moveX, moveY, 33, 33); // Gray circle
} // Empty draw() keeps the program running

void mousePressed() {
  //rect(mouseX, mouseY, 33, 33);//clear by draw,do not draw event callback
}
void mouseMoved() { // Move gray circle
  moveX = mouseX;
  moveY = mouseY;
}

void mouseDragged() { // Move black circle
  dragX = mouseX;
  dragY = mouseY;
}
